The present invention relates to a fuel control system for an automobile engine for controlling fuel supply so that fuel may be cut at the time of deceleration of the engine.
2. Description of the Prior Art
Japanese Patent Publication No. 58-20374 discloses a fuel control system for an automobile engine, in which when a throttle valve is fully closed and the engine speed is faster than a predetermined speed, the system judges that the engine is in an engine deceleration condition and cuts fuel supply to fuel injectors, thereby improving fuel consumption. When the deceleration condition is removed, the amount of fuel to be supplied to the engine is restored to an amount less than the normal amount corresponding to the running conditions of the engine at the time of removal of the deceleration condition. Thereafter, the amount of fuel to be supplied is gradually increased to the normal amount, and consequently, a sudden increase in the amount of fuel supply, which is caused by the restoration at the time of removal of the deceleration condition, is restored, thus preventing the occurrence of torque shock.
In an engine equipped with an automatic transmission, the engine output is transmitted to the transmission through a torque converter. Accordingly, such restoration in fuel supply causes less torque shock on a transmission output shaft in an engine equipped with an automatic transmission than in an engine equipped with a manual transmission.
Because of this, if the amount of the reduction of the fuel supply is established on the basis of the engine equipped with the manual transmission, the amount of the reduction is too great for the engine equipped with the automatic transmission, and therefore engine stalling occasionally takes place when a shift lever is shifted from the neutral position to the drive position. More specifically, if a driver is under the false impression that the shift lever is in the drive position while the shift lever is actually in the neutral position, he will probably step on an accelerator pedal to start and accelerate his car. In that event, the engine is brought into the so-called racing condition. When he confusedly operates the shift lever from the neutral position to the drive position, the engine speed rapidly decreases, thus occasionally resulting in stalling of the engine. One reason for this is that since the engine speed, that is a criterion for executing the reduction in supply fuel is generally higher in the neutral position than in the drive position, the reduction in fuel supply usually takes place when the shift lever is shifted to the drive position. In that event, if the amount of reduction fuel supply is too great, the rise of torque is dull. Another reason is that the load of the driving system acts on the engine.
On the other hand, if the amount of the reduction of the fuel supply is established set on the basis of the engine equipped with the automatic transmission, the amount of the reduction is too little for the engine equipped with the manual transmission. Accordingly, the torque shock acting on the transmission output shaft caused by the aforementioned restoration cannot be restrained.